Jacking assembly

ABSTRACT

A jacking assembly for moving a load, in steps, axially of a pipe comprises two pawl boxes having lateral platens and which are mounted at axially spaced positions on the pipe. The pawls of the boxes slope towards the pipe and exert a grip on it which allows relative movement between the boxes and the pipe to occur in one direction only. Inflatable hoses connected to a low pressure water supply are sandwiched between the platens and exert a thrust, when dilated, which increases nonlinearly with water pressure, to move whichever of the pawl boxes is carrying the load. This movement, which provides the working stroke, is followed by a recovery stroke during which the pawl box not carrying the load is moved up to the other pawl box under the action of springs or a second inflatable hose. The assembly is able to lift a heavy load with a low pressure water supply and has no moving seals. Its operation in parallel with other such assemblies is also described for house building and slip forming purposes.

FIELD OF THE INVENTION

This invention relates to a jacking assembly for moving a load, insteps, lengthwise of an elongated member such as a bar, and which iscapable of being operated hydraulically with other jacks. Such jackingassemblies are useful in house construction and in slipforming.

STATE OF THE ART

Australian Pat. No. 261,151 discloses a jacking assembly as describedabove. It utilises two independently moveable gripping parts which eachengage the bar and are capable of being slid in one direction only,along it. Movement of the gripping parts in the reverse direction underthe action of the thrust of the load, is prevented by sets of teethwhich bite into the wall of the bar under the thrust of the load. Pairsof hydraulic rams constructed as piston and cylinder units, areconnected between the two gripping parts and are expanded to advance onegripping part, and thus the load, and are then retracted to draw theother gripping part towards the advanced gripping part. For each cycleof operation of the hydraulic rams the jacking assembly advances onestep along the bar.

Jacking assemblies as described above are used in slip-forming and canalso be used, when connected hydraulically in parallel, to lift heavyloads such as concrete slabs. However such jacking assemblies arerelatively expensive and require costly ancilliary equipment.

The expense of the jacking assembly stems, in part, from the piston andcylinder units used. The fitting of a piston in a cylinder necessitatesclose manufacturing tolerances and the use of expensive moving pistonseals. If a number of such assemblies are operated in parallel thefailure of a seal in one of the hydraulic units results in the liftingoperation being held up until the defective unit is repaired orreplaced. As the site of use may be remote from repair facilities, thefailure of a seal is a serious matter and high quality seals and a highstandard of maintenance of the units are essential.

A further factor which increases the cost is the relative complexity ofthe piston and cylinder units. During lifting of a heavy load by anumber of such units operated in parallel, it is usual for the load tobe unevenly distributed amongst the jacking assemblies. This results insome of the hydraulic units reaching the ends of their strokes beforeothers. The increase in pressure in the hydraulic system necessary toensure that all of the units execute the same length of stroke, has tobe bypassed from the units which have already completed their strokes asotherwise they could be seriously damaged. This by-passing is achievedby providing the units with valves which close when the end of thestroke is reached to isolate the cylinder of the unit from a furtherpressure increase. Were this not done the stops which limit the pistonstroke could be strained. The provision of such valves and by-passfacilities increases the cost of the units.

A further reason why such units are expensive is that the manufacturingcost of a unit increases rapidly with its size because the length of thecostly piston seal and thus the likelihood of it failing, also increaseswith the diameter of the unit. For these reasons, quite apart fromconsiderations of weight and compactness, fluid pressure-operatedjacking assemblies are always used in conjunction with high pressurehydraulic systems which normally operate at pressures of 800 pounds persquare inch or above. This entails the use of specially constructedpressure pumps and high pressure lines as well as expensive pistonseals.

Despite the above disadvantages hydraulically operated jackingassemblies have found wide acceptance on building sites. However damageto the moving seals of the piston and cylinder units by abrasive dirtwhich is always present on a building site, is commonplace and hashitherto been regarded as an unavoidable disadvantage which has to beaccepted if hydraulically operated jacking assemblies are to be used.

OBJECT OF THE INVENTION

An object of this invention is the provision of an improved jackingassembly capable of being used with others to lift large loads.

THE INVENTION

In accordance with the present invention .[.a fluid-pressure operatedjacking assembly for moving a load, in steps, comprises;.].

.[.a. two gripping parts adapted to be mounted at axially spacedpositions on the member,.].

.[.b. gripping devices mounted on each part and which grip the member ina way which allows relative axial movement in one direction only betweenthe member and the parts,.].

.[.c. fluid-pressure operated thrusting equipment for forciblyseparating the two parts in response to the admission of a fluid underpressure to the equipment during a working stroke, and.].

.[.d. means for forcing the two parts towards one another to execute arecovery stroke which follows the working stroke; in which assembly saidequipment incorporates a flexible, inflatable, but non-elastic bagshaped progressively to reduce its area of contact with the two parts asit dilates so that the ratio of thrust to fluid pressure diminishes asthe two parts of the assembly move apart. The bag is preferably a hosesection having its longitudinal axis lying in a plane which isperpendicular to the direction of the axis of the member convenientlyformed by a pole or pipe..]. .Iadd.a fluid operated jacking assemblysuitable for moving a load, in steps, axially of an elongate memberhaving a substantially constant cross-section the assembly comprising:

said elongate member, two parts adapted to be slidably mounted ataxially spaced positions on the member;

pawl devices mounted on each of said parts and engagable with theelongate member in a way which permits relative axial movement in onedirection only between the elongate member and said parts;

fluid-pressure operated means for forcibly separating the two parts inresponse to admission of a pressurised fluid to said means during aworking stroke, and means comprising a least one inflatable bag locatedbetween and in contact with the two parts and, in operation of thejacking assembly, adjacent the elongate member, the bag being flexiblebut non-elastic so that the area of contact of the bag with the twoparts diminishes progressively with increasing admission of pressurisedfluid and consequential dilation of the bag and, recovery means forforcing the two parts towards one another to execute a recovery strokefollowing the working stroke and release of fluid pressure from saidfluid pressure operated means. .Iaddend.

PREFERRED FEATURES OF THE INVENTION

When the jacking assembly is operating, the thrust produced by theexpanding bag causes movement of one of the two parts and, during thesubsequent contraction of the bag, the other of the two parts is moved.[.up to.]. .Iadd.towards .Iaddend.the first part by the.[.retraction.]. .Iadd.recovery .Iaddend.means which may .[.be.]..Iadd.act by .Iaddend.gravity, a resilient spring, or a secondinflatable bag which is operated alternatively with the first bag andacts between the two parts but in the opposite sense (on each part) tothe first bag.

The jacking assembly in one construction draws one pipe out of anotherso as to produce a telescopic strut. By turning the assembly upsidedown, it may be used to climb the member.

The advantages of the invention is that no moving seals are used and lowfluid pressures in the range 28 p.s.i. .Iadd.to .Iaddend.160 p.s.i. arepossible. The bag which operates the assembly simply inflates and thendeflates and, if it is constructed as a hose which assumes a circularcross-section when dilated, the upward jacking thrust is a function ofthe hose length and dilation. .[.When the jacking assembly is operatedin parallel with other jacking assemblies to lift a load, the increasein thrust exerted by each jacking assembly diminishes in accordance withthe inflation of the flexible bag..]. .Iadd.Thus, in order to lift aload with the jacking assembly, an increase in hydraulic pressure withinthe bag must be provided to offset the smaller contact area caused bydilation of the bag. .Iaddend.This stems from the fact that the more thebag is inflated, the less becomes the areas of it in contact with thetwo parts and which are urging them apart. A number of such jacksoperating in parallel exhibits a self-levelling ability automaticallywithout requiring bypass valves and without straining stroke-limitingstops because the bags can be designed to have a high bursting strengthand can, if required, be fitted inside one another to increase thebursting strength still further. When one bag is fully dilated underload, the fluid pressure--either pneumatic or hydraulic--applied to it,can be increased substantially without .Iadd.significantly.Iaddend.increasing the upward thrust .[.of the.]. .Iadd.provided by the.Iaddend.jacking assembly. The stroke lengths of all of the jackingassemblies can .[.therfore.]. .Iadd.therefore .Iaddend.be maintained.Iadd.relatively .Iaddend.constant over .Iadd.a .Iaddend.wide fluidpressure range. A further advantage of the jacking assembly is that itsupward thrust can be increased or diminished by adjusting the areas ofthe two parts in contact with the bag. If the bag is in the form of ahose length sandwiched between platens on the two parts, the adjustmentcan be effected by .[.placing a washer between the two parts or by.].simply changing the dimensions of the platens in contact with the hose.They may, for example, be provided with sliding ends which enable thelengths of the platens to be .[.foreshortened.]..Iadd.adjusted.Iaddend..

The devices for allowing relative movement axially of the elongatedmember conveniently comprise pawls which are inclined to the axis of theelongated members and bite into it. The other ends of the pawls arehinged slackly to the jacking assembly in a way which allows the pawlsto slew slightly if the jacking assembly is turned around the pipe.Preferably a simple abutment hinge is used. This allows the jackingassembly to be moved in the direction normally resisted by the pawls,provided that such movement is accompanied by rotation of the jackingassembly which causes the pawls to slew slightly. Controlled lowering ofthe assembly is therefore possible without the risk of injury to thepersonnel handling it.

Conveniently the pawls are provided with switch arms accessible outsideof the jacking assembly and which allow the pawls to be moved out ofengagement with the pipe or other member. This enables the load to`float` on the bags when the switch arms of one part are operated andthe bags are dilated.

For lifting very heavy loads, a symmetrical arrangement of four pawls ineach of the two parts may be used. If only one pair of opposed pawls isused in each part, there can be a tendancy for the pawls to bend thecross-section of the pipe into an oval. A cruciform configurationcounteracts this tendancy.

One may also fill the pipe of the assembly engaged by the pawls withconcrete to increase its overall strength to resist bending as well asits resistance to inward deformation. This can be done .[.at.]. .Iadd.on.Iaddend.site so that the pipe is transported while hollow and thereforelight. A concrete filled metal pipe is naturally also cheaper .Iadd.toconstruct .Iaddend.than a solid .[.one to construct.]. .Iadd.metalone.Iaddend..

.[.The.]. .Iadd.Preferred forms of the .Iaddend.invention will now bedescribed in more detail, by way of examples with reference to theaccompanying drawings:

IN THE DRAWINGS

FIG. 1 is a front view of a jacking assembly for climbing a pipe whichis shown partially broken away, the position of bags or hoses in theassembly being shown in dotted outline in their collapsed condition;

FIG. 2 is a side view of FIG. 1;

FIG. 3 is a plan view of FIG. 1, the end portions of the hoses togetherwith some pipe connections between them being shown in broken outline;

FIG. 4 is a fragmentary cross-section through FIG. 3, taken on the lineand in the direction indicated by the arrows IV--IV in FIG. 3;

FIG. 5 is a cross section through FIG. 4, and taken in the directionindicated by the arrows V--V in FIG. 4;

FIG. 6 shows the jacking assembly of FIG. 2 in more detail and with thehoses expanded;

FIG. 7 shows the assembly of FIGS. 1-6 turned upside down and used todraw the inner of two telescopically arranged pipes out of the outerpipe on which the assembly rests, in order to form an expanding pier;

FIG. 8 illustrates how the self-levelling property of the jackingassembly can be used to maintain level a load being lifted despitesubsidence of one of the foundations supporting it during lifting;

FIG. 9, is a cross-section through an inflatable bag of the jackingassembly at two stages of inflation in order to explain, more clearly,the self-levelling property of the jacking assembly;

FIG. 10 shows in simplified form a modification of part of the assemblyto increase the height of the stroke or lift of the jack;

FIG. 11 shows an alternative arrangement to that shown in FIG. 10, inorder to increase the height of the lift of the jack and its speed ofoperation;

FIG. 12 is a simplified plan view of a jacking assembly incorporatingthe modification of FIG. 11, and shows hydraulic connections to theinflatable hoses;

FIG. 13 is a plan view of a further embodiment of jacking assembly usedto lift heavier loads than is possible with the assemblies shown inFIGS. 1-6;

FIG. 14 is a side view of FIG. 13, greatly simplified and shows apacking plate used to vary the lift of the jacking assembly;

FIG. 15 shows a stage in the construction of a two-storey house;

.[.FIGS. 16 to 18 show comparatively, operating curves of the jack ofthe invention and a conventional piston and cylinder jack;.].

.Iadd.FIG. 16 shows characteristic curves for a typical jacking assemblyin accordance with the present invention .Iaddend.

FIG. .[.19.]. .Iadd.17 .Iaddend.shows a stage in the raising of aconcrete factory roof.

FIG. .[.20.]. .Iadd.18 .Iaddend.shows how a roof may be lifted, one sideat a time;

FIG. .[.21.]. .Iadd.19 .Iaddend.shows how a pole, formed by a mild steelpipe, of a climbing jack also made out of mild steel, can be stiffenedby associated scaffolding;

FIG. .[.22.]. .Iadd.20 .Iaddend.shows various ways of lifting a concreteroof;

FIG. .[.23.]. .Iadd.21 .Iaddend.shows an expandible platen usable in thejacking assembly;

FIG. .[.24.]. .Iadd.22 .Iaddend.shows how two bags can be usedrespectively to expand and contract the jacking assembly; and,

FIG. .[.25.]. .Iadd.23 .Iaddend.shows how two jacking assemblies fixedtogether back to back and one reversed with respect to the other, can beused to pull slip-formers up around a pipe and then, after fixing thejacking assemblies, the pipe can be pulled up with respect to theslipformers.

In the accompanying drawings of the different embodiments, correspondingparts are similarly referenced, the reference being identified from oneanother by suffixes. Parts bearing corresponding references, but withdifferent suffixes are to be understood as operating similarly and theirdescription is not therefore repeated in detail.

PREFERRED EMBODIMENT

The jacking assembly 1 shown in simplified form in FIG. 1 comprises anupper part 2 and a lower part 3 which are mounted on a steel pipe 4. Theparts 2 and 3 have mounted between them two short sections of hose 6 and7 which are shown in the collapsed condition and which are made fromflexible non-elastic plastics material. The hoses 6 and 7 are connectedhydraulically in parallel and can be dilated by filling them with waterunder pressure. As the hoses expand, they assume a flattened cylindricalconfiguration, and push the two parts 2 and 3 of the jacking assemblyapart. This separation movement is guided by side lugs 8 arranged inpairs at each side of the jacking assembly and which have aligned boresthrough which steel bolts 10 are a slack fit. Lock nuts 11 on the endsof the bolts 10 determine the extent of the separation of the two partsof the jacking assembly. Separation of the two parts 2 and 3 occursagainst the resilience of a pair of coil springs 12 located,respectively, one at each end of the assembly and connected at theirends to brackets 13 fixed respectively to the two ends of each part ofthe assembly.

The upper and lower parts 2 and 3 of the jacking assembly are identical,apart from the provision of a lateral arm 16 on the upper part, and thusone part 2 only will be described.

The upper part 2 comprises a pawl box 15 of square cross-section andwhich is closed at its ends by plates 17 each of which contains anupright slot 18, from which projects a pawl switch arm 20. The centre ofthe pawl box is provided with a vertical circular hole 21 .Iadd.(FIG.3).Iaddend., which is a clearance fit around the periphery of the pipe 4which passes through it.

At each side of the pawl box 15 is a platen 22 comprising two tubes 23of square cross-section which are welded to one another and to the sidewall of the pawl box 15. As is clearly shown in FIG. 1, when the pawlboxes of the upper and lower parts 2 and 3 of the jacking assembly aretouching one another their platens 22 are spaced slightly so that thehoses 6 and 7 are not squashed between them.

Each pawl box houses a pair of pawls one of which is shown in FIG. 4 andreferenced 25. These pawls slope inwardly and downwardly towards thecentral region of the pawl box and they have their adjacent ends shapedto provide a sharp circular edge 26, which, apart from its end-portions27, is complementary to the surface of the pipe 4 when the pawl is inthe position shown in FIG. 4. The end portions of the edge 26 are cutacross as shown at 27. The switch arm 20 of the pawl is welded to anintermediate position 28 on its .[.upper.]. .Iadd.under.Iaddend.surface, and the end of the pawl opposite the pipe 4 nests in acorner provided between an abutment wall 29 welded to the inside of thepawl box 15 and the pawl box roof to provide an abutment hinge.

Each pawl 25 has welded to it at an intermediate position a transversepin 30. The ends of the pin 30 project beyond the side of the pawl 25,but terminate short of the side walls of the pawl box 15. The projectingends of the pin 30 provide supports for respective coiled portions of awire spring 31. The intermediate portion of this spring extends acrossthe under face of the pawl 25 from the pin 30, and its end portions arebowed downwardly and forwardly inside the pawl box so that they engageits floor and thereby urge the pawl 25 against the pipe 4. The pawl 25may be moved away from the pipe 4 by lifting the pawl arm 20 and a catch36 is provided on the plate 17 of the pawl box to hold it in its liftedposition.

The two diametrically arranged pawls 25 in the pawl box are as clearlyshown in FIG. 6. These pawls allow each of the two parts 2, 3 of thejacking assembly to ascend the pipe 4 but bite into the wall of the pipeto resist its descent. The greater the load on the jacking assembly, thegreater is the force tending ot keep the pawls in contact with the pipe4. In practice, the angle made by the pawls with the pipe 4 can bevaried and is normally about 30° to the horizontal.

Reverting to FIG. 3, the two hoses 6 and 7 are closed at their ends bybeing clamped to the periphery of cylindrical metal cups 40. The cups 40at one end of the jacking assembly are connected by a branch pipeconnection 41 having a T-junction in it to allow water under pressure of100lbs. p.s.i. to be admitted by way of a flexible conduit .[.41.]..Iadd.42.Iaddend..

OPERATION OF PREFERRED EMBODIMENT

The operation of the jacking assembly will now be described.

The jacking assembly 1 of FIG. 2 carries .[.the weight.]. .Iadd.a load.Iaddend.which is to be lifted in steps up the pipe 4 and the downward.[.thrust of the weight.]. .Iadd.force due to the load .Iaddend.isresisted by the two sets of pawls 25 which slope downwardly and havetheir lower .[.cuved.]. .Iadd.curved .Iaddend.ends pressed tightlyagainst the wall of the pipe 4 with a force proportional to the load onthe jacking assembly.

Water at 100 lbs. p.s.i. pressure is admitted to the hoses 6 and 7 toexpand them. As they are arranged one each side of the pipe 4 theirexpansion exerts a balanced thrust tending to separate the two parts 2and 3. As the lower part 3 is prevented by its pawls 25 from movingdownwardly, the upper part 2 is forced up the pipe and the lower edgesof its pawls 25 within the pawl box 15 trail against the surface of thepipe 4.

As the hoses expand, their surface areas in contact with the platensdiminish. This is apparent from FIG. 9 which shows in the left-handsketch a fully dilated hose 6 in section and in the right hand sketch ahalf dilated hose. The upward thrust is a function of the hydraulicpressure P inside the hose and its area in contact with the platens 22.In the case of the left-hand sketch this area is referenced a which isless than the corresponding area b in the right hand sketch. .[.The rateof increase of the upward thrust of the jack therefore diminishes as itsstroke increases..]. .Iadd.Therefore, in order to lift a load with thejacking assembly, an increase in hydraulic pressure within the bag mustbe provided to offset the smaller contact area caused by dilation of thebag. .Iaddend.The length of the stroke is determined by the extent towhich separation of the two parts 2 .Iadd.and .Iaddend.3 is permitted bythe positions of the lock nuts 11 on the guide bolts 10. It can also beadjusted by introducing a plate of the appropriate thickness on thesurfaces of the two lower platens 22, so that the hoses 6, .Iadd.and.Iaddend.7 lie on the plate which effectively reduces the spacingbetween each pair of platens.

At the end of the upward movement of the upper part 2 of the jackingassembly, the hydraulic pressure in the hoses is reduced, and, as isclear from FIG. 6, the load .[.of.]. .Iadd.supported by .Iaddend.thejacking assembly is carried by the upper pair of pawls 25. The lowerpart 3 of the jacking assembly now carries no load and the coil springs12 draw it upwardly beneath the upper part 2. This is accompanied byexpulsion of the water from the hoses 6 and 7. The pawls 25 associatedwith the lower part 3 trail against the wall of the pipe 4 during thisupward movement.

In the above cycle of movement, the jack may be advanced about 21/2inches while carrying a load of 6 tons and using two hoses each of whichhas a width measured horizontally of 15 centimeters and a length of 38centimeters. The hose is made of non-elastic fabric-reinforced flexibleplastics material and its end portions are turned back on themselves andheld on each cup 40 so that a .[.self-sealing.]. .Iadd.sealed.Iaddend.connection is made. The hosing material is marketed inAustralia under the trade name "stay flat" or "roll flat". The jackingassembly can be stepped up the pipe of FIG. 6 indefinitely. In theunlikely event of one pair of pawls failing, the other pair of pawls iscapable of carrying the weight so that there is 100% safety factor builtinto the jacking assembly. The maximum distance a load can drop as aresult of the failure of one pair of pawls, is the separation distanceof the two pawl boxes 15. This can be adjusted to suit the load. Inpractice if such a set of pawls is not sufficiently sharp to grip thepipe, it slips at the beginning of a lift and this is immediatelynoticed by the apparent failure of the jacking assembly to operate. Thepawls can then be replaced.

At the end of the lift, the weight of the load can be transferred to asuitable support and the jacking assembly lowered down the pipe 4. Thetwo sets of pawls resist this lowering as the weight of the assembly isabout 50 lbs so that, if allowed to fall freely, it could be dangerous.However, free fall of the jacking assembly cannot take place unless bothpairs of pawls are moved out of engagement with the pipe 4. This ispossible by raising both of the pawl switch arms 20 (see FIGS. 4 and 5)but this would not be done in normal circumstances as it is preferableto have controlled lowering of the jacking assembly.

Controlled lowering of the assembly is possible because of the way inwhich the pawls 25 are mounted in the pawl boxes 15. Turning to FIG. 5,it will be seen that as the pawl pins 30 do not extend the full width ofthe pawl box 15, the effect of rotating the pawl box about the axis ofthe pipe is to cause the pawls 25 to slew slightly in a horizontaldirection so that the pipe 4 is engaged by one of the edge portions 27of the pawl 25 only. This engagement, coupled with the weight of thejacking assembly, is sufficient to prevent vertical descent of theassembly down the pipe but, if the jacking assembly 15 continues to berocked about the pipe 4 the engaging corner portion 27 prescribes adownwardly spiralling path at an angle of about 15° to the horizontal.Thus the jacking assembly can be lowered by disengaging the top pair ofpawls 25 and holding them disengaged by securing the switch arms to thecatches 36 so that the jacking assembly weight is carried by the lowerpair of pawls only. By twisting the jacking assembly back and fortharound the pipe it can be spiralled down the pipe by one person in acontrolled manner and if the assembly is let go, the pawls reassumetheir operating positions on the outside of the pipe 4 and prevent theassembly from falling further.

FIRST MODIFICATION OF PREFERRED EMBODIMENT

FIG. 7 shows a telescopic strut or pier utilising the jacking assemblyof the previous figures and which is turned upside down. The part of thejacking assembly of FIG. 7 corresponding to those of earlier figures aresimilarly referenced but with the suffix 1 applied to their numerals.

The expanding pier has the pipe 4₁ telescopically arranged inside aslightly wider pipe 40. The part 2₁ of the jacking assembly, as a resultof it being turned upside down, rests on the top rim of the pipe 40 andthe pawls 25₁ are inclined upwardly towards the pipe 4₁ as is clearlyshown in FIG. 7.

When the hose 7₁ is expanded, the engagement of the part 2₁ of theassembly with the top of the pipe 40 prevents it from moving downwardly,and the pawls 25₁ of the .[.part 3₁ .]. .Iadd.Parts 2₁ and 3₁.Iaddend.being inclined upwardly against the wall of the inner pipe 4₁, preventslippage there between. Expansion of the hose 7₁, is thereforeaccompanied by upward movement of the part 3₁ together with the pipe 4₁.The pier therefore is expanded through a step determined by theavailable lengths of the bolts 10₁.

At the end of the expansion step, the hydraulic pressure in the hose 7₁is relieved so that the spring 12₁ pull the part 3₁ back down the pipe4₁ until the two pawl boxes 15₁ are again in contact. This return strokeof the part 3, is not accompanied by the downward movement of the.[.pupe.]. .Iadd.pipe .Iaddend.4₁ as it is held in relation to the lowerpipe 40 by the lower pair of pawls 25₁. The readmission of water underpressure to the hoses of the jacking assembly causes it to expand thepier by a second step.

The advantage of the expanding pier of FIG. 7 is that the hydraulicconnections to the hoses do not move during the extension of the pier,whereas in the arrangement shown in the FIGS. 1-6, the hydraulicconnections climb, with the jacking assembly, up the pipe 4.

When the load carried by the expanding pier has been raised to therequired height, it can be transferred to a suitable support and thepawl switch arms operated to allow the pipe 4₁ to descend back into thepipe 40 so that the jack is ready for re-use.

An important feature of the jacks of the invention is that, whenoperated in parallel, they have a self leveling ability. This isimportant when lifting heavy loads which are weak in bending strength,such as reinforced concrete.

At the present time a reinforced concrete floor of a building which isto be located above ground level, is often built at ground level andthen raised. If the lift applied to the reinforced concrete does notremain constant at each point of lifting, the concrete is subjected to abending .[.movement.]. .Iadd.moment .Iaddend.and will crack. Inpractice, is is not possible to guarantee that the weight of theconcrete will be evenly distributed between the lifting points becauseinevitably some movement of the supports occurs. For this reason thethickness of the concrete has to be increased to prevent it breaking upwith the uneveness of the distribution of lift anticipated during normallifting with cranes or individual manually-controlled jacks. Theadditional concrete which must be used to enable lifting to take placesafely, is expensive and increases the overall weight of the structureunnecessarily. Even then it is common-place for concrete floors liftedinto position to be found to be cracked in the corners, and, inpractice, this cracking is ignored.

The self-balancing ability of the jacking assembly of the invention,when used in parallel with others, enables it to lift a reinforcedconcrete floor slab with a guaranteed maximum deflection. Inconsequence, it can be more cheaply manufactured than is at presentpossible and the invention therefore facilitates the use of therelatively safe technique of building parts of a structure at groundlevel and then raising them into the operating positions when finished.

FIG. 8 illustrates diagrammatically a heavy load 50 being lifted by sixtelescopically arranged piers 51 of the type described with reference toFIG. 7. The same references are used in FIG. 8 as in FIG. 7. A load maybe a concrete block although, in the diagrammatic view shown in FIG. 8it is a house roof.

The hoses of the jacking assemblies are connected in parallel so thatthey are pulsed together by hydraulic pressure which is regulated by acontroller 52 arranged to one side of the load 50, and generated by awater pump .[.53.]. .Iadd.52 .Iaddend.driven by an electric motor.[.54.]. .Iadd.53.Iaddend.. For convenience only six piers are shown butit will be understood that many more may be provided.

The outer pipe 40 of each pier rests on a foundation 55. These are shownat ground level with the exception of the foundation 55a which it isassumed has subsided a short distance during the previous lifting strokeof the jacking assembly. The subsidence distance is, of course, greatlyexaggerated in FIG. 8 because it cannot be greater than the strokelength of the jacking assembly, as otherwise the only load on it wouldbe that of the pipe 40 and the jacking assembly in an unloadedcondition. The effect of the subsidence of the foundation 55a, whichwould normally not be more than 1/4 inch, is to reduce the share of theload carried by the associated jacking assembly. This load reduction isassociated with a slight increase in load on all of the other jackingassemblies.

During the next hose expansion step of the jacking assemblies, the loadon the subsided pier is less than on all of the other piers. Therefore,during the expansion of the hoses, the pair of hoses associated with thesubsided pier will expand faster than the other hoses because suchexpansion is occurring against a smaller downward thrust. The effect ofthis is that the subsided pier is .[.expanded.]. .Iadd.extended.Iaddend.faster than the others until the load is once again sharedequally between them. There is thus a self-levelling effect on the roofprovided that the hoses are not expanded to an extent that a set ofstops, which limit the extent of separation of the two parts, limits theexpansion of the hoses and forces all the assemblies to execute the samelength of stroke. The system shown in FIG. 8 has been shown in practiceto be able to lift a roof weighing between four and six tons 15 feetwith less than 1/4 inch mis-alignment at the end of the total lift ascompared with what it was at the beginning.

It will be appreciated that if the jacks of the invention were replacedby high-pressure piston and cylinder jacks, the same effects are notobtained. The conventional hydraulic jack using a piston and cylinderunit will, if connected in parallel with the other similar jacks eachcarrying a different part of the same load, alter the position of theload until it is equally divided between the jacks, i.e. each jack isidentically loaded. One can counteract this, of course, by providingeach jack with a stop to limit its extension. The jacks most lightlyloaded then abut their stops first. Increasing the hydraulic pressurewould then allow the remaining jacks to reach their stops later. Howevera feature of the piston and cylinder jack is that the thrust it exertsvaries linearly, with the hydraulic pressure applied.[.as shown in FIG.16 in the curve AB.].. As the loading applied to each jack of a setsupporting a roof is never exactly the same as the loading applied tothe other, one must either vary the hydraulic pressure applied to eachjack individually, if it is to go up the same step as the others, whichis not practical, or increase the hydraulic pressure after some of thejacks have reached the ends of their upward strokes and are abuttingtheir stops so that the remainder, more heavily-loaded jacks, carry outthe same stroke. This technique involves a considerable amount oftilting of the load during each step and is also not practical, unlessbypass valves and circuits are provided on the jacks, because the effectof increasing the hydraulic pressure inside a fully extended jack candamage it, bearing in mind that each jack may be lifting 10,000 lbs ormore and using high hydraulic pressures.

The jacking assembly of the invention does not have the abovedisadvantage as will now be explained with reference to FIG. 9. As isapparent from this figure, the areas of the hoses in contact with theplatens 22 .[.diminishes.]. .Iadd.diminish .Iaddend.non-linearly as thelifting stroke of the jack progresses (FIG. 18) with a commensuratereduction in the .[.rate of increase of the.]. upward thrust. Thus, ifthe hydraulic pressure is increased, straining of the mechanical partsof the jack is avoided as the hose assumes a slightly more roundedshape. This reduces the upward thrusting areas of the hose so that thereis a negligible increase in upward thrust. In practice the jackingassemblies are operated between almost complete flattening of the hose,and expansion of the hose to about five sixths of the diameter..[.When.]. .Iadd.Once .Iaddend.this expansion is obtained, negligiblefurther increase in upward thrust is obtainable. The pressure of thehydraulic system can then be increased so that other jacking assembliescan complete their strokes without straining the mechanical connectionsof the jacks already at the ends of their strokes.

It will be appreciated that the jacking assemblies shown in FIGS. 1 to 6have the same advantages when operated in parallel, as the jackingassembly described in reference FIGS. 7 and 8. However, they have yet afurther advantage when lifting a roof. The arm 16, shown in FIG. 1, istied at each end to a wire fixed to the roof. If the roof is suckedupwards by windforces, the upward force is applied to the end of the arm16 and cants the upper part 2 of the jacking assembly sideways at rightangles to the direction of the pawls. This canting movement causes thecorner edges of the circular hole in the pawl box 15, through which thepipe 4 passes, to bite into the wall of the pipe and resist upwardmovement of the jacking assembly. Although ties to the ground may alsobe provided for the roof, they have been found to be unnecessary as thelocking effect obtained by pulling the arm 16 upwards is sufficient toresist very strong upward forces on the roof.

SECOND MODIFICATION OF PREFERRED EMBODIMENT

FIG. 10 shows a way of doubling the lift obtained by the hose. For.[.somplicity.]. .Iadd.simplicity .Iaddend., only two platens 22₂ areshown and a length of hose 6₂ is shown doubled back on itself betweenthem. Hydraulic connections to the hose are made at 42₂ joining the twocups 40₂. A plate 60₃ is sandwiched between the two overlapping portionsof the hose 6₂ so that they do not roll over one another when dilated,and the plate, in plan, has the shape illustrated in FIG. 12 at 60₃ andfits between the lower and upper parts of the jacking assembly with thepipe, engaged by the pawls, passing through a hole in the centre of theplate 60₃. Thus, when the plate 60₃ is incorporated into the jackingassembly, its opposite sides lie between the two pairs of platens. Theplate 60₃ is centrally apertured to accommodate the pipe 4₃ (see FIG.12).

A U-shaped copper tube 61 lies in the return bend of the hose in FIG.10, and is positioned by cords which extend through the hose to theclosure cups 40₂. These cords prevent the tube 61 displacing so thatwhen the hoses 6₂ are collapsed hydraulic liquid admitted to it isevenly distributed between both halves of the hose 6₂.

THIRD MODIFICATION OF PREFERRED EMBODIMENT

FIG. 11 shows a method of increasing the lift still further. Here thehose 6₃ is doubled back on itself twice so that three times the lift isobtained. The two platens between which the lift is exerted are shown at22₃, and two plates 60₃ are used to keep the horizontal hose sectionsseparate from one another. The advantage of the arrangement shown inFIG. 11 is apparent from FIG. 12 where the hydraulic connections areillustrated. It will be seen from this figure that hydraulic fluid canbe admitted conveniently from both ends of the two hoses of the jackingassembly so that a relatively large lift is obtained with littleadditional apparatus or piping to the hoses being necessary.

FIG. 15 shows the application of a number of jacking assemblies as shownin FIGS. 1 to 6, to the construction to a two storey house. FIG. 15 isextremely diagrammatic. The house is constructed by first building itsfoundation 70 and then building, at ground level, the roof 71 on top ofthe foundation. An array of pipes 4₄ are mounted on the foundation 70,two of these pipes being shown, and the jacking assemblies 1₄ are thenused to raise the roof 71 to the level of the first floor.

The first floor, referenced 72 is next constructed at ground level underthe protection of the roof 71. When the first floor is completed, it ismounted on a further set of jacking assemblies 1₅ and these assembliesare identical to and connected hydraulically in parallel with theassemblies 1₄. Both sets of assemblies are operated in unison so thatthe roof 71 and the first floor 72 are raised simultaneously to theirrequired positions. The ground floor of the house can then beconstructed on the foundations 70 and the walls put in if this has notalready taken place. As the jacks have .[.the.]. .Iadd.an.Iaddend.identical stroke, the first floor and the roof of the house canbe raised simultaneously while maintaining the spacing between them.Indeed, a multi-storey building is capable of being constructed usingthis concept. As an alternative to this system of building, one set onlyof jacking assemblies could be used. The roof is first raised to itsdesired spacing from the floor beneath it which is then constructed,with the walls between the floor and the roof, at ground level. Thejacking assemblies are then lowered so that the weight of the roof iscarried by the walls. The jacking assemblies are next secured to thefloor from above, and the structure comprising the roof, first floor andintervening walls, is raised bodily to its required position. The floorbeneath together with its side walls can be constructed and the sequencerepeated to build a multi-storey building. This system of constructionis particularly well suited to buildings having reinforced concretefloors.

FIG. .[.19.]. .Iadd.17 .Iaddend.shows the construction of a very largebuilding such as a factory, warehouse or railway station. The buildinghas its foundations laid first, as shown at 80. A roof, which may bereinforced concrete, is then constructed at ground level on thefoundations. Building a roof at ground level has the advantage thatcuring of the concrete is better because the temperature and humidity ofthe environment in which the concrete is setting, can be more easilycontrolled at ground level. This is particularly important in coldclimates. The roof is referenced 81 in FIG. 17 and is shown lifted halfway to its operating position.

An array of vertical pipes 4₆ passes through the roof and each hasmounted on it a jacking assembly 1₆. These are each located beneath theroof and carry beneath them a slip former 82 surrounding the pipe 4₆.Concrete is admitted to the slip former 82 by means of a lateral pipesystem 83.

When the roof 81 has been constructed, it is gradually lifted up thepipes 4₆ by simultaneous operation of the jacking assemblies 1₆associated with them as is described with reference to FIG. 8. As theroof is slowly raised, concrete is admitted to the slip formers 82, andthis concrete has quick drying characteristics so that as the roofascends under the control of a timer controlling the lifting system, theconcrete hardens inside the slip formers 82 to form a casing surroundingeach of the pipes 4₆. Thus as the roof 81 rises, pipe reinforcedconcrete pillars are progressively formed beneath it by the slip formers82. The walls of the structure may finally be built into positionbetween the reinforced pillars, and after transfer of the weight of theroof to the pillars, the remaining portions of the piping 4₆ can be cutaway and the jacking assemblies 1₆ and slipformers 82 removed.

SECOND EMBODIMENT

FIGS. 13 and 14 shows a modification of the jacking assembly shown inFIGS. 1 to 6, which is particularly well suited to lifting heavy loadssuch as concrete. The jacking assembly is basically the same as thatshown in FIGS. 1-6 except that the platens 22₇ are formed by three metaltubes of rectangular cross section projecting at right angles to thesides of the pawl boxes 15₇. These tubes are referenced 90, 91 and 92 inFIGS. 13 and 14. The wall of the pawl box facing the tubes 91 iswindowed and the parts are arranged in a cruciform pattern with thepawls 25₇, within the pawl box, arranged at right angles to similarlymounted pawls 93 arranged within the tubes 91 and projecting through thewindows of the pawl box into engagement with the pipe 4₇. As there is adegree of overlap between the curved corner edges of the pawls whichgrip the pipe 4₇ the pawl pair 93 is arranged to grip the pipe 4₇ about1/2 inch above the pawl pair 25₇.

The advantage of the cruciform arrangement of pawls associated with eachof the two parts of the jacking assembly is that twice the resistance todownward movement of each part of the assembly is obtained together witha balanced application of forces of the wall of the pipe 4₇. Anytendancy for the pipe to be compressed from a circular cross-section toan eliptical cross section under heavy loads, and caused by one set ofpawls, is resisted by the corresponding set of pawls arrangedperpendicularly thereto.

The way in which the pawls are mounted in the pawl boxes and the tubes91, is identical to that shown in FIGS. 4 and 5 and will not be againdescribed. However, the brackets 13₇ are duplicated at the ends of thetubes 91 so that each jacking part has four brackets. Likewise thesprings 12₇ are duplicated as is clearly shown in FIG. 13. As is clearfrom this figure the switch arms associated with the individual pawlsproject from the ends of the pawl box 15₇ and also through slotsprovided in end plates covering the exposed ends of the tubes 91 so thatindividual disengagement of the pawls from the pipe 1₇ is possible.

FIRST MODIFICATION OF SECOND EMBODIMENT

FIG. 14 shows a plate 60 which can be placed and appropriately fixed bya bolt or other attachment to the top surface of the platen 22₇ orbetween the pawl boxes in order to vary the spacing between the twoplatens 22₇. This facility can be useful for reducing the lift of theindividual jacking assemblies.

FIG. .[.20.]. .Iadd.18 .Iaddend.shows how the speed of lifting of ahouse roof may be doubled. Each side of the roof is supported on a lineof jacking piers as described with reference to FIG. 7. One pier of thefirst line is shown at 100 and the corresponding pier of the second lineis shown at 101. The hoses of the first line are connected hydraulicallyin parallel to receive water under pressure from a change-over valve 103which is supplied with water from a pump 104 driven by a motor 105. Thepump has its suction inlet connected to a water reservoir tank 106 whichis fed with water exhausting from two exhaust ports 107 of thechange-over valve 103. A timer 108 operates the change-over valve sothat it simultaneously connects, in alternation, one line of piers toreceive water from the pump while providing exhaust connections forenabling the water in the hoses of the other line to flow into thereservoir 106. When the system of FIG. .[.20.]. .Iadd.18 .Iaddend.is inuse, first one side of the roof is jacked up 21/2 inches and then theother side. The advantages obtained are that the pump 104 operatescontinuously, instead of intermittently. The hoses of one set of piersare collapsing while those of the other set of piers are dilating, aclosed hydraulic circuit with a relatively small reservoir is all thatis required. .[.The speed of lifting can be increased because the loadto be lifted during each lifting stroke is halved..].

At the end of the lift, the walls can be erected and, if necessary,capped with wet cement onto which the roof is lowered to form animprint. This is carried out by inflating both sets of hosessimultaneously so that the entire weight of the roof is carried by them.The upper set of pawls 25 (FIG. 7) can then be disengaged from the pipe4, so that, on controlled release of the hydraulic pressure in thehoses, the roof gently subsides onto the wet cement. Once the imprint ofthe roof seating is made in the cement, the roof can be raised again andlowered permanently on to the cement after it has set. In this way aneven distribution of the roof weight on the walls is assured andcracking of the brickwork--which is commonplace when .Iadd.a.Iaddend.separately constructed roof is lowered on to it does not occur.Once the roof weight is carried by the walls, the telescopic piers canbe removed. The jacking assembly described is capable of providing ahorizontal traction as well as a vertical lift and may be used to pushor pull a load. Currently available hydraulic piston and cylinder jacksfor house lifting use hydraulic pressures of several thousand pounds persquare inch, whereas the jacking assemblies above described use lowpressure of only about 28 to 160 lbs per square inch, although it may bereadily adapted to high pressure working, if desired, simply byincreasing the strength of the hoses.

FIG. .[.19.]. .Iadd.17 .Iaddend.shows one way of incorporating the pipesof the jacking assembly usefully into the structure of a building whichit is being used to construct. Both the pole-climbing jack assembly ofFIGS. 1 to 6 and the telescopic pier of FIG. 7 can be likewise used.

FIG. .[.21.]. .Iadd.19 .Iaddend.shows a pole-climbing jack assembly 110ascending a pipe 111 composed of pipe sections having spigot and socketconnections enabling them to be fitted into one another as the buildinggrows. The building comprises a roof 112 constructed at ground level andwhich provides protection for personnel working beneath it. The weightof the roof 112 is carried by a number of jack assemblies, such as thejack assembly 110, mounted above the roof. As the roof is raised, thewalls 115 of the building are constructed of brick, steel orcombination. A second pipe 111A alongside the pipe 111, is built intothe wall 115 to strengthen it and is attached by braces 114 to the pipe111 and to .Iadd.scaffolding .Iaddend.113. In this way, the scaffolding.Iadd.113 .Iaddend.and pipe 111A braces the pipes 111 of the jackingassembly against lateral deflection.

In the case of the telescopic expanding pier, the outer pipe 40 (FIG. 7)can have its foot cemented into the concrete foundations of the buildingbeing erected so that no sideways stability problems occur. The roof orother structure being lifted is supported, temporarily, by a prop, whenit is at the required height and the jacking assembly is no longerrequired. An attachment plate fitted to the roof and engaged by the topof the pipe 4 (FIG. 7), is disengaged from the pipe, which is thenlowered into the outer pipe 40 by a suitable tackle from the attachmentplate. The upper and lower parts 2, 3 of the jacking assembly are thenremoved. The inner pipe 4, is then drawn out of the outer pipe 40 by thetackle and connected permanently, for example by welding, to theattachment plate. The upper rim of the outer pipe 40 is also weldedpermanently to the inner pipe .[.40.]. .Iadd.41 .Iaddend.so that the twopipes form a rigid vertical structure connected securely to the roof atits top end and bedded in the foundations of the building at its lowerend.

FIG. .[.21.]. .Iadd.20 .Iaddend.shows very diagrammatically a concreteroof constructed at ground level of inverted arches of waffleconstruction, and being lifted into position in two different ways. Inthe first way, the pipes of the jacking assemblies pass through holes inthe waffle, as shown at 120, with the jack 121 itself, located beneaththe arch as shown on the left hand side of the FIG. 1. A slip former 122is attached beneath one leg 123 of the roof arch and is fed withconcrete so that as the roof ascends, a concrete pillar 124 is formedsimultaneously by the slip former 122 to support the weight of the roof.The pipe of the jacking assembly is composed of sections havingtelescopically interfitting spigots and sockets at their ends. Aconsiderable height of roof lift can be achieved in this way and thejacking assembly is easily removed when the desired height of the roofis attained.

The right hand side of FIG. .[.21.]. .Iadd.20 .Iaddend.shows analternative way which does not involve perforating the roof and providesreinforcement for the pillars. Corresponding parts to those alreadydescribed are similarly referenced but are primed. The roof is liftedfrom above by the jacking assembly the pipe of which extends down theend face of the roof alongside the leg 123₁. As the lift proceeds, theslip former 122¹ forms a concrete case around the pipe so that theresultant support pillar 124¹ is of reinforced construction. Oncompletion of the lift, the projecting pipe section is cut off with thelifting parts of the jacking assembly and weight of the roof is carriedby the slip-formed pillar 124¹.

The above described jacking assemblies are versatile in use and, withoutmodification, can be used as pole-climbing jacks or for telescopicallyarranged expanding piers. They can work in dirty, gritty or greasyconditions which is not practical with .[.a.]. moving seal jacksutilizing a piston in a cylinder, and can be serviced by a screwdriveralone. Finally, by extending the lengths of the hoses and platens thelifting capacities can be easily varied.

FIG. .[.23.]. .Iadd.21 .Iaddend.shows how a platen 200 of a jackingassembly 201 may be provided with telescopically retractable ends 202 tovary the length of it in contact with the hose and thus the upwardthrust exerted by it on the load when the hose expands. Not only can theupward thrust .[.for.]. .Iadd.exerted by .Iaddend.a jacking assemblysubjected to a given hydraulic pressure be finely adjusted in this way,it also allows the centre G of upward thrust on the platen to be moved(to G₁ in the figure) to compensate for eccentric loading of the jackingassembly with an off-centre load. The pawl box and other parts of theassembly of FIG. 23 are similar to those shown in the jacking assemblyof FIG. 3.

Also, the lifting capacities can be varied by reducing the liftingstroke as is apparent from the characteristic curves of FIG. .[.18.]..Iadd.16.Iaddend..

FIG. .[.24.]. .Iadd.22 .Iaddend.shows a variation of previousembodiments which all show the recovery stroke of the two parts of thejacking assembly being controlled by springs. In FIG. .[.24.]..Iadd.22.Iaddend., instead of springs, a short hose section .[.210.]..Iadd.220 .Iaddend.is used. The jacking assembly comprises an upper part211 and a lower part 212 which are each equipped with pawl boxes 213 asis previous embodiments, and with platens 214 extending horizontally ateach side of a pipe 215 up which the jacking assembly is to climb. Thetwo pawl boxes 213 contain pawls 216 which slope downwardly towards oneanother and grip the wall of the pipe 215. Between the two pairs ofplatens 214 are located respective hose sections 217.

Mounted beneath the lower part of the jacking assembly is a carrier 218.As shown, this is identical to the other parts of the jacking assemblyand likewise contains pawls but these are not strictly necessary. Thecarrier 218 is connected by steel bars 219 to the upper part of thejacking assembly. A second expandible hose section 220 is locatedbetween the platens of the carrier 218 and the platens above. The hose220 shown is of the same length as the hose 217. However it wouldnormally be substantially shorter as it does not participate in thejacking up of the load but serves only to expel water forcibly from thehose 217 during the contraction stroke of the jacking assembly. Thehoses 217, 220 are connected to a change-over valve 221 which isconnected to an 80 lb/in² water pump.

The jacking assembly illustrated performs its working stroke by dilationof the hose 217. This forces the upper part 211 upwards so that theassembly commences to climb the pipe 215. At the end of the workingstroke the switch 221 is operated, perhaps by a timer so as to beautomatic, and the hose 217 is connected through the switch to exhaustand the hose 220 is dilated. This forces the lower part 212 upwardlyfrom the carrier 218 to expel, forcibly, the water from the hose 217. Asthe thrust the hose 220 must exert to do this is very much less than theload on the jacking assembly, the hose 220 can, in practice, be verymuch smaller in length than the hose 217 although it should dilate tothe same diameter.

FIG. .[.25.]. .Iadd.23 .Iaddend.shows the use of the invention inslipforming. A concrete pillar 300 is poured by encasing its outlinewith a tubular slip former 301 suspended by ties 302 from a jackingassembly shown generally and diagrammatically at 303. The jackingassembly 303 comprises two assemblies 304 of the type shown in FIG. 6but one of them is turned upside down with respect to the other and theneighbouring platens 306 of the two assemblies are fixed together byclamps 305.

Each assembly 304 has hoses 307 which are hydraulically connected inparallel with one other. The upper assembly 304 has pawls 308 whichslope upwardly and engage a pipe 309 which is vertically mounted on thecentre-line of the pillar 300 but is about six meters long.

The lower assembly 304 has pawls 310 which are held inoperative by theassociated switch arms 311 which are held by catches (not shown).

Scaffolding 315 extends upwards alongside the position of the pillar300.

FIG. .[.25.]. .Iadd.23 .Iaddend.shows the assembly 304 set to lift thepipe 309 from the centre of the last poured section of the concretepillar 300. This is done when the concrete has become firm but is notyet sufficiently hard to prevent the pipe 309 from being extracted fromit. The extraction may be assisted by prior sheathing the pipe 309 witha pair of semi-cylindrical thin plastics shells from which the pipeslips easily and which remain in the concrete. The shells are formedinternally and externally with .[.circumferntially.]..Iadd.circumferentially .Iaddend.extending closely spaced grooves andribs to provide grips.

Prior to lifting the pipe 309 the ties 302 are attached firmly to thescaffolding as at 321. The hoses 307 are then inflated. As the pawls 310do not touch the pipe the lower hoses 307 does not do any work. Howeverthe hoses of the upper assembly cause the pipe 309 to be drawn upwardlyout of the concrete 300 until only a short section of its length remainsbeneath the level of the top of the concrete 300. The extraction of thepipe takes place in steps as has already been described with referenceto FIG. 7 above.

When the pipe 309 is raised to its new position it can be held inposition by providing its lower end with outwardly sprung pawls whichlock into the grooves of the plastics shells and are inclined so thatthey prevent its descent in much the same way as the inclinations of thepawls of the pawl boxes prevent descent of the jacking assembly.

As an alternative to providing bottom pawls on the pipe, sand may bepoured through the interior of the pipe 309 to fill up the hole left byit in the concrete 300 so that the pipe 309 rests at its lower rim onthe sand or .[.xement.]. .Iadd.cement .Iaddend.to provide a firm basefor it during the following lifting stage.

At the commencement of the following lifting stage the attachment 321between the ties 302 and the scaffolding 315 is disconnected.

The pawls 310 of the lower assembly have their switch arms moveddownwardly so that the pawls engage the wall of the pipe 309. The pawlsof the upper assembly are then moved out of engagement with the pipe 309by operating their associated switch arms 330 and the hoses 307 are thenagain pulsed.

The two lower sets of pawls 310 now operate as described above withreference to FIG. 6 when the hoses 307 are pulsed, to cause the assembly303 to climb the pipe 309. As the assembly 303 ascends, it draws up theslip-forming casing 301 around the pipe 309 to a new position inreadiness for pouring of the concrete of the next section. Before thistakes place, two new plastics semi-cylindrical shells are placed aroundthe pipe 309.

The above described technique allows a pillar to be poured in sectionsby a slip forming process without requiring unnecessary metal work to belocked in the concrete and which may have to be removed, by expensivehydraulically operated traction equipment, using current-day.[.proceedures.]. .Iadd.procedures .Iaddend.which are both expensive andoften unsuccessful

Adjustment of the spacing between the two parts of the jacking assemblyat the completion of the recovery stroke can be effected by placingadjustable stops between the pawl boxes. Such stops may comprise platesof varying thickness, as described and illustrated, or stepped wedges,or adjustable bolts screwed into one of the pawl boxes.

I claimed: .[.1. A fluid operated jacking assembly suitable for moving aload, in steps, axially of an elongated member the assembly comprising:in unison to lower the roof onto the top of the wall..]. .[.16. Anassembly as claimed in claim 1, in which the fluid pressure operatedthrusting equipment comprises hose sections arranged one each side ofthe position of the longitudinal axis of the member and having theirlongitudinal axes arranged in a plane perpendicular to that of the axis,the hose sections being each doubled back on itself and aroundrespective marginal portions of a separation plate which is freelymoveable between the two parts and separates the two doubled-backportions of each hose section so that they do not bear on one anotherwhen dilated, means being provided for maintaining a fluid path betweenthe two doubled-back portions of each hose section when the hose isflattened..]. .[.17. An assembly as claimed in claim 1 in which eachpart is of cruciform configuration when viewed in the direction ofelongation of the member and is provided with two pawl pairs arrangedperpendicularly to one another and being shaped to engage around themember at nearly the same position along its length so that the member,at that position, is subjected to substantially balanced, radiallyinwardly directed, thrusts from the pawls..]. .Iadd.
 18. A fluidoperated jacking assembly suitable for moving a load, in steps, axiallyof an elongate member having a substantially constant cross section, theassembly comprising:said elongate member, two parts adapted to beslidably mounted at axially spaced positions on the member; pawl devicesmounted on each of said parts and engagable with the elongate member ina way which permits relative axial movement in one direction onlybetween the elongate member and said parts; fluid-pressure operatedmeans for forcibly separating the two parts in response to admission ofa pressurised fluid to said means during a working stroke, said meanscomprising at least one inflatable bag located between and in contactwith the two parts and, in operation of the jacking assembly, adjacentthe elongate member, the bag being flexible but non-elastic so that thearea of contact of the bag with the two parts diminishes progressivelywith increasing admission of pressurised fluid and consequentialdilation of the bag, and recover means for forcing the two parts towardsone another to execute a recovery stroke following the working stroke,and release of fluid pressure from said fluid pressure operated means..Iaddend..Iadd.
 19. An assembly as claimed in claim 18, in which saidbag comprises tubular hose means having a longitudinal axis which liesin a plane perpendicular to the axis of the elongate member. .Iaddend..Iadd.
 20. An assembly as claimed in claim 19, in which said bagcomprises two lengths of hose connected hydraulically in parallel, inwhich said parts of the assembly have respective pairs of platens, andin which each of said hose lengths lies between two of said platens atopposite sides of the elongate member and with its axis in a planeperpendicular to the elongate member, and having means for admittingsaid pressurised fluid to said bag, said admitting means being attachedto said bag and separate from two parts. .Iaddend..Iadd.
 21. An assemblyas claimed in claim 20, in which said hose lengths each have oppositeend-portions which extend beyond the ends of said platens and each saidplaten is provided with adjustable extension means to vary the length ofthe platen in contact with the hose length. .Iaddend..Iadd.
 22. Anassembly as claimed in claim 21, in which said recovery means includes acoiled tension spring connected between the two parts. .Iaddend..Iadd.23. An assembly as claimed in claim 18, including a carrier rigidlyconnected to one of said parts and lying on the opposite side of theother of said parts to said one part, and said recovery means comprisesan inflatable element located between said carrier and said other partwhereby inflation of the element forces said other part towards said onepart to expel fluid from said bag during said recovery stroke..Iaddend..Iadd.
 24. An assembly as claimed in claim 23, in which theinflatable element comprises a hose portion having a longitudinal axislying in a plane perpendicular to the longitudinal axis of said elongatemember. .Iaddend..Iadd.
 25. An assembly as claimed in claim 18, in whicheach of said pawl devices comprises a pawl box defining aligned openingsthrough which said elongate member passes and having platens whichextend laterally away from opposite sides of each said pawl box, saidbag comprising at least one tubular hose lying in a plane perpendicularto the longitudinal axis of said elongate member and sandwiched betweensaid two parts, arranged to bear on said platen portions thereof..Iaddend..Iadd.
 26. An assembly as claimed in claim 25, in which thepawl box contains pawls, and springs which are provided for said pawlsfor urging them to positions at which their ends engage opposite sides,respectively, of the elongate member at opposite positions, the lengthsof said pawls being such that they make substantially the same acuteangle with the longitudinal axis of the elongate member, and in whicheach pawl is provided with a rigid switch arm extending through anopening in the pawl box which is movable from outside the pawl box todisengage said each pawl from said elongate member. .Iaddend..Iadd. 27.An assembly as claimed in claim 26, in which said pawls comprise flatsteel plates each formed at one end with an arcuate, sharp concave edgeto grip the periphery of a circular section said elongate member, andwhich assembly also comprises abutment walls in said pawl box, abutmenthinges formed at the opposite end of each said pawl from said concaveedge by the engagement of each said pawl opposite end with respectivesaid abutment walls, and slant-cut corner edges at each said one end ofsaid pawls; in which assembly the width of each said pawls issufficiently small for there to be a clearance between the sides of eachsaid pawl and the inside of the pawl box to enable each said pawl toslew during controlled lowering of the assembly, the pawl box also beingprovided with catches for engaging with said switch arms so as to holdthe respective pawls in positions whereby they are disengaged from saidelongate member during lowering. .Iaddend..Iadd.
 28. An assembly asclaimed in claim 18, arranged in "-back-to-back-" combination with asecond similar assembly, clamping means connecting together the adjacentsaid parts of the respective assemblies, control means being provided toenable said parts of the two assemblies to be selectively effective, andthe fluid pressure operated means of the two assemblies being connectedfor parallel inflation and deflation. .Iaddend..Iadd.
 29. An assembly asclaimed in claim 18, in combination with a pair of telescopicallyarranged pipes of which the smaller diameter pipe comprises saidelongate member and is engaged by the pawl devices while the largerdiameter pipe provides a support for the assembly, whereby operation ofthe assembly extends the smaller diameter pipe in steps from the largerdiameter pipe to provide a telescopically extendible strut..Iaddend..Iadd.
 30. An assembly as claimed in claim 18, including guideswhich prevent the two said parts from twisting with respect to oneanother, and adjustable stops between the two parts which allow them toseparate and come together to predetermined adjustable extents..Iaddend..Iadd.
 31. An assembly as claimed in claim 18, mounted on avertical pole constituting said elongate member arranged parallel toother vertical such poles each having a similar operating assemblymounted on it, the fluid pressure operated means of the assemblies beinghydraulically connected for parallel operation in a closed water circuitwhich includes a pump and a reservoir tank. .Iaddend..Iadd.
 32. Anassembly as claimed in claim 18, in which the fluid pressure operatedmeans comprises hose sections arranged one each side of the longitudinalaxis of the member and having their longitudinal axes arranged in aplane perpendicular to that of the axis, the hose sections being eachdoubled back on itself and around respective marginal portions of aseparation plate which is freely movable between the two parts andseparates the two doubled-back portions of each hose section so thatthey do not bear directly on one another when dilated, means beingprovided for maintaining a fluid path between the two doubled-backportions of each hose section when the hose is flattened..Iaddend..Iadd.
 33. An assembly as claimed in claim 18, in which eachsaid part is of cruciform configuration when viewed in the axialdirection of said elongate member and is provided with two pawl pairsarranged perpendicularly to one another and being shaped to engagearound the elongate member at nearly the same position along its lengthso that the member, at that position, is subjected to substantiallybalanced, radially inwardly directed, forces from the pawls. .Iaddend.